The Vincent J. Coates Proteomics/Mass Spectrometry Laboratory (P/MSL) serves the proteomics needs of the greater UC Berkeley and California Institute of Quantitative Biology community. We request the replacement of an obsolete ion trap mass spectrometer with a new state of the art linear ion trap mass spectrometer equipped with the latest improvements in peptide fragmentation technology. The instrument requested is a Thermo Fisher LTQ XL linear ion trap mass spectrometer equipped with an ETD fragmentation unit. The P/MSL serves a community of more than 363 laboratories on the UC Berkeley campus with an average of 27 laboratories per year using its services. The most common analysis is multidimensional chromatographic separation of complex mixtures of peptides with simultaneous peptide identification (MudPIT). The P/MSL has aided many laboratories to identify the protein contents of complex mixtures, to find sites of post-translational modification and to observe protein metabolism. These laboratories are virtually all engaged in NIH supported projects with impact on human health. PUBLIC HEALTH RELEVANCE: The QB3/UC Berkeley Vincent J. Coates proteomics/mass spectrometry laboratory (P/MSL) serves a community of at least 363 laboratories in three schools and colleges at UC Berkeley, plus numerous other laboratories. Proteomics services are crucial to a wide variety of research projects that impact human health. To continue to supply state of the art proteomics services, the P/MSL needs to replace its aging mass spectrometer with a new instrument.